Polymerization catalyst compositions and method of utilizing



United States Patent M 3,287,302 POLYIVIERIZATION CATALYST COMPOSITIONSAND METHOD OF UTILIZING Herman B. Wagner, Perkasie, Pa., assignor toTile Council of America, Inc., New York, N.Y., a corporation of New YorkNo Drawing. Continuation of application Ser. No. 597,098, July 11, 1956.This application Jan. 21, 1963, Ser. No. 252,603

4 Claims. (Cl. 260-28) This application is a continuation of mycopending application U.S. Serial No. 597,098, filed July 11, 1956.

The present invention relates to improved catalyst compositionsparticularly useful in certain synthetic resin polymerization reactionsand to improved methods of utilizing synthetic resin catalysts thatnormally cause very rapid polymerization, such that the reaction isunder better control.

It has previously been known that certain catalysts cause thepolymerization of particular synthetic resins at a very rapid rate, therate of polymerization often being so rapid that it is almost impossibleto completely incorporate the catalyst in the resin by simple mixingbefore the reaction takes place. Reaction may be so rapid that it isalso difiicult, if not impossible, to place the polymerizing resin insome desired location or make use of it in some desired manner thatrequires pouring or spreading since the material becomes solidified toosoon. Furthermore, some of these polymerization reactions are highlyexothermic to the extent that decomposition of the resin system tends tooccur, sometimes with explosive violence.

In many instances it would be desirable to make use of the catalyststhat bring about the too-rapid polymerization if the polymerization ratecould be retarded sufficiently to overcome the above recited objections.

One object of the present invention is to provide improved catalystcompositions useful in certain rapid polymerization reactions.

Another object is to provide an improved method of utilizing a catalystwhich normally causes too-rapid polymerization to occur.

In achieving the above stated objects, the present invention includes asa feature thereof an improved method of utilizing catalysts thatnonnally cause a polymerizable system to polymerize at an undesirablerapid rate, such that the reaction is slowed down and under bettercontrol. The catalyst, if a liquid, is absorbed within a substance whichis inert both with respect to the catalyst and to the substance which isto be polymerized. The inert substance is of a porous nature and is inparticulate form. By porous is meant any structure which includes voidscapable of absorbing a liquid whether the voids are spherical, columnar,or flat as in -a laminated body. The particles, which are impregnatedwith the catalyst, are coated with an easily meltable material throughwhich the catalyst c-an diiiuse very slowly and which melts and releasesmore catalyst when the temperature of the system rises high enough toexceed the melting temperature of the coating material.

An example of a system in which the improved compositions and methods ofthe present invention can be used to great advantage is the epoxyresins. These resins may be described generally as condensation productsof poly-arylepoxy compounds and derivatives of such polymers. Examplesof manufacture of these resins are found in US. Patents 2,324,483 and2,444,333 to Castan. Any of the epoxy resins may be polymerized by theprocesses of the present invention.

Although polymerization of the epoxy resins is usually brought about byusing catalysts which cause sub- Patented Nov. 22, 1966 stantiallycomplete polymerization in anywhere from about 15 minutes to severalhours, there are certain catalysts which are capable of causingpractically instantaneous polymerization. Since the reaction is anexothermic one, a great deal of heat is liberated in a short interval oftime and the temperature of the system may rise so high thatdecomposition of the resin occurs. There is also the danger of explosionand, even though this undesirable result is avoided, the reaction isstill so rapid that the properties of the polymer are seriouslyimpaired. On the other hand, the use of .the previously utilized sloweracting cat-alysts requires time delays which are undesirably long inmany applications.

Examples of catalysts of the rapid acting type for epoxy resins are:halides, i.e., boron tri-fluoride, -iodide, bromide, or, -chloride.Using the improved compositions and methods of the present invention, ithas been found possible to slow down the polymerization reactionsufiiciently such that the reaction, instead of being substantiallyinstantaneous, as it would norm-ally be if the catalyst and resin weremerely mixed together without taking any special precautions, can bemade to take place over a time interval from about one minute to severalminutes thus giving sufiicient time to pour the resincatalyst mixturefrom the mixing vessel to molds, to spread it as a coating, or to use itin other ways such as for bonding tile.

The rapid-acting catalyst, which is preferably in liquid form, isabsorbed within a carrier which is in the form of a particulatesubstance which is both inert and immiscible with respect to thecatalyst and the resin which is being polymerized. Using any of theboron halide-s as the catalyst and the epoxy resins as the system to bepolymerized, examples of suitable carrier materials are pumice andinfusorial earth. The carrier particles, with the catalyst absorbed inthe pores thereof, are then coated with a substance having a relativelylow melting temperature. The paraffin hydrocarbon waxes are generallysuitable for the coating material. In general, the coating material mustnot only be easily meltable but must also be inert and immiscible withrespect to both the catalyst and the resin.

A quantity of catalyst-impregnated carrier particles containingsuflicient catalyst to polymerize a particular quantity of resin is thenmixed with the unpolymerized resin and the mixture is transferred to anappropriate mold, form, or other site where it is desired to have thepolymerization take place. Following this, the temperature of the systemis raised sufficiently to exceed the melting temperature of the coatingmaterial. Transition of the coating substance from the solid to theliquid state unseals the carrier pores, allowing outward diffusion ofthe catalyst and mixing thereof with the substance to be polymerized. Ifthe polymerization reaction is sufficiently exothermic, as is usuallythe case with the epoxy resins, enough of the catalyst may diffusethrough the meltable coating, before it is melted, to cause a slow risein temperature such that the melting temperature of the coating materialis soon reached without the application of external heat. In othercases, external heat may have to be applied.

Instead of directly mixing the catalyst-impregnated carrier particleswith the substance to be polymerized, the particles may first bedispersed in some form of diluent, such as another resin, which iscompatible with the polymerized substance. The diluent should not bereactive with the catalyst and it may take any one of several forms,such as a plasticiser or other resin modifier.

Example 1 5 grams of boron trifluoride-ethyl ether (45% BF were mixedtogether with 20.5 grams of dry powdered pumice (particle size: 50% on,50% through 200 mesh). To this was added a solution of 2 grams ofeicosane (melting point: 35.5 to 37.5 degrees centigrade) in grams ofhexane. After thorough mixing of the pumice particles with the solution,the thick slurry was poured onto a flat glas tray and the hexane allowedto evaporate, leaving :behind the eicosane-coated pumice particles. Witha layer of slurry about to minutes at room temperature sufficed forevaporation of the hexane to the atmosphere. The total weight of now dryparticles recovered was 26.8 grams, compared to a calculated weight of27.5 grams.

One gram of these catalyst-containing particles was then dispersed bythorough stirring in four grams of a saturated polyester resin (ThiokolChem. Corp. ZL-207, for example) toward which the boron trifluoridecatalyst is inert. This dispersion was added to six grams of a liquidepoxide-type resin (Shell Chemical Co. Epon Resin 828) and stirredvigorously for twenty seconds. Epon 828 is a condensation product ofbisphenol A and epichlorohydrin, The liquid composition was then quicklypoured into a small mold and hardened within 90 seconds time, measuredfrom the initial combination of the two liquid portions. A thermometerplaced in a similar mixture showed a slow temperature rise' from degreescentigrade initially, to a temperature of 37 degrees centigrade oneminute after mixing. A sudden rise to a temperature of 115 degreescentigrade then occurred, the mix being observed to rapidly solidify atthis point.

, Example 2 A procedure similar to that described in Example 1 wasfollowed with the following changes: 15 gram-s of pumice were usedrather than the 20 grams noted in Example 1; in place of the eicosanethere were used four grams of a paraffin wax with melting point in therange 50 to 55 degrees centigrade. 23.2 grams of dry catalyst particleswere obtained, compared to a calculated 24.0 grams.

0.8 gram of this material was dispersed by vigorous stirring in one gramof saturated polyester (ZL-207) and then fifteen additional grams of thepolyester added. This slurry was then added to eighteen grams of theepoxy resin and stirred rapidly. A slow temperature rise from 24 degreescentigrade to 52 degrees centigrade occurred over a period of twominutes, followed by a very rapid temperature rise to 110 degreescentigrade as solidification occurred.

Example 3 The same liquid compositions described above were cooled to 10degrees centigrade before combining. After mixing the two liquids,approximately three minutes were required for the mixture to solidify,thus providing an extended Working time.

Example 4 Four grams of the catalyst particles were dispersed as abovein the polyester resin (50 grams). To this slurry were added 6 grams ofa 5 0/50 titanium dioxide pigment,

polyester resin dispersion. This slurry was then added to a solution offour grams of xylene in grams of the epoxide resin, the xylene additionbeing made to obtain a reduced viscosity for easier pouring. The mixturewas then poured rapidly into the joints G4," spaces) in a square arrayof ceramic wall tile. Solidification occurred within two minutes,yielding a hard, strong bond between the tiles.

Besides the parafiin waxes, many other types of easily meltable materialmay 'be used as the coating for the particulate carrier. Examples arefatty acids, fats, greases, natural resins, certain synthetic resinscapable of forming polymeric films, such as polyethylene and polyvinylchloride, and even low-melting temperature metallic compositions suchasWoods metal. For most uses it is preferred that the coating materialhave a melting temperature from about 20 degrees centigrade to about 80degrees centigrade. It must, of course, not be soluble in the catalyst,

The invention is also useful with resin systems other than the epoxytype. Other resins, such as the alkyds, wln'ch are also capable of veryrapid polymerization with the evolution of heat, in the presence ofcatalysts, can be utilized.

Having thus described the invention, what is claimed is:

1. A method of polymerizing an epoxy type resin in the presence of aboron halide catalyst which normally causes the polymerization to occuralmost instantaneously, said method comprising, absorbing the catalystin liquid form, within a porous, particulate, inert substance; coatingthe particles of said inert substance with a paraffin wax, mixing thecoated particles with said epoxy resin which is in liquid, unpolymerizedform; and permitting the polymerization reaction to occur with evolutionof heat at a retarded rate as the catalyst is slowly released from saidparticles.

2. A method according to claim 1 in which said inert substance ispowdered pumice.

3. A method according to claim 2 in which said wax is eicosane.

4. A method according to claim 1 in which the waxcoated particles arefirst dispersed in a saturated polyester resin before mixing with saidepoxy resin.

References Cited by the Examiner UNITED STATES PATENTS 2,326,984 8/1943Tomlin 260793 2,343,835 3/1944 Smith et al. 260-752 2,406,869 9/1946Upham 252-433 2,528,932 11/1950 Wiles et al. 2,653,925 9/1953 Olin26079.5

FOREIGN PATENTS 583,471 12/1946 Great Britain.

MORRIS LIEBMAN, Primary Examiner.

B. A. AMERNICK, Assistant Examiner.

1. A METHOD OF POLYMERIZING AN EPOXY TYPE RESIN IN THE PRESENCE OF ABORON HALIDE CATALYST WHICH NORMALLY CAUSES THE POLYMERIZATION TO OCCURALMOST INSTANTANEOUSLY, SAID METHOD COMPRISING, ABSORBING THE CATALYSTIN LIQUID FORM, WITHIN A POROUS, PARTICULATE, INERT SUBSTANCE, COATINGTHE PARTICLES OF SAID INERT SUBSTANCE WITH A PARAFFIN WAX, MIXING THECOATED PARTICLES, WITH SAID EPOXY RESIN WHICH IS IN LIQUID,UNPOLYMERIZED FORM; AND PERMITTING THE POLYMERIZATION REACTION TO OCCURWITH EVOLUTION OF HEAT AT A RETARDED RATE AS THE CATALYST IS SLOWLYRELEASED FROM SAID PARTICLES.